Transfer and fixing method



1961 E. WALKUP 2,995,085

TRANSFER AND FIXING METHOD Filed Feb. 23, 1954 FIG. I

35 lECI INVENTOR.

LEWIS E. WALKUP Y FM gflmkm ATTORNEY United States Patent 2,995,985TRANSFER AND FIXING METHOD Lewis E. Walkup, Columbus, Ohio, assignor, bymesne amignmeuts, to Haloid Xerox Inc., a corporation 'of New York FiledFeb. 23, 1954, Ser. No. 411,747 7 Claims. (Cl. 101-4492) This inventionrelates to production of high-quality permanent images throughxerography and more particularly to methods and apparatus for thetransfer and fixing of developed xerographic images.

In the art of xerography it is usual to place an electrostatic chargeupon the surface of a xerographic plate which is composed of aconductive backing member and a photoconductive insulating coating. Thecoating is a good insulator in darkness and will retain theelectrostatic charge placed thereon. However, an area of the chargedsurface will be quickly discharged upon exposure to light. When acharged plate is exposed to a pattern of light an electrostatic latentimage is produced on the plate surface. The latent image may bedeveloped by cascading particles across the surface of the xerographicplate, particles which will readily adhere to charged areas on the platesurface. Usually, this developed image body of particles is thentransferred electrostatically to another surface, and is there fixedthrough heat fusing. However, this method of transfer and fixing issubject to certain limitations and is not always the method of choice,particularly for high quality photographic reproduction. It is thereforean object of this invention to disclose means, methods and apparatus forthe production of high quality transfers of developed Xerogr-aphicimages. It is another object of this invention to provide means, methodsand apparatus for fixing or fusing the transferred image.

A difficulty which has existed in the art of xerography is that oftransferring the developed xerographic image to an electricallyconducting surface such as zinc or aluminum. The use of electrostatictransfer to a conducting surface is presently very complicated anddeterioration of quality of image may sometimes result. Where otherknown techniques are used the quality of the transferred image again maybe substantially poorer than the originally developed xerographic image.It is therefore another object of this invention to provide means,methods and apparatus for transferring a developed xerographic image toa conducting surface without loss of quality.

A further object of this invention is that of improving the quality oftransfer obtainable when transferring a developed xerographic image to asubstantially rigid surface such as for example a zinc lithographicplate, thereby facilitating the use of xerography in new fields.

In transferring a developed xerographic image to some surfaces, such asa conducting or a rigid surface or the like, diflicult problems offusing or fixing the image permanently to the surfaces are encountered,and it is there fore still another object of this invention to providenovel means, methods and apparatus for permanently fusing a xerographicimage to a surface.

Additional objects of the invention, will in part, be obvious and will,in part, become apparent from the following specification and drawingsin which:

FIG. 1 is a plan view of a xerographic powder image on a surface;

FIG. 2 is a flow step showing the transfer of a xerographic powder imageto an intermediate transfer material; and

FIG. 3 is a side view in cross section showing transfer apparatusaccording to one embodiment of the invention.

Referring to the drawings, in FIG. 1 a developed xerographic image 11 isshown on surface which may be a xerographic plate or any other surfaceon which a developed xerographic image has been placed. The developedxerographic image 11 shown in FIG. 1 is mirror reverse reading.Conventional xerography will produce a mirror reverse reading image, orif prisms and optical systems are used, a direct reading image. Forpurposes of describing this invention reference will be made to image 11shown in the figures as reverse reading, but it is to be remembered thata direct reading developed xerographic image can be produced if desiredand it is intended that the description which follows also includes adirect reading image.

FIG. 2 shows the transfer of the developed xerographic image 11 fromsurface 10 to sheet 12. The transferred image on sheet 12 is designatedgenerally as 13. As can be seen in FIG. 2 the mirror reverse image 11becomes a direct reading image 13 on transfer to another base and it canbe said that a transfer from one surface to another throughout thisinvention results in a change of the direction of reading of the image.

The transfer to sheet 12 may be brought about in a number of ways suchas through the use of electrostatics, or other process known to those inthe art, or the like. One preferred method of transfer is disclosed inthe now abandoned application Serial No. 397,917, filed December 14,1953 by Andrus and bearing the name Pressure Transfer of XerographicImages and continued in US. Patent 2,843,499 which issued on July 15,1958 hearing the same name and inventor and includes transfer of animage body by pressure transfer to a softened dye transfer paper or thelike. Sheet 12 should be any surface capable of accepting the image suchas any sheet or web, or the like, or such surfaces as are disclosed insaid pending application. This includes, but is in no way limited, topapers, films, gelatin coated surfaces, coated surfaces in general,plastics, cloths, and other forms of sheet material.

FIG. 3 represents one embodiment of a transfer apparatus, andalthoughthis invention is described in terms of this apparatus, it is tobe understood that any other apparatus capable of achieving the same endresults is intended to be included. As is shown in this drawing, sheet12 is placed with image 13 exposed on transfer table i5 and is movedunder vapor applicator 16 and into rollers 27 and 28 mounted in andabove transfer table 15. Transfer surface 30, such as a sheet or web towhich xerographic image 13 is transferred, is brought into contact withsheet 12 and image 13 as sheet 12 and transfer surface 30 feed throughrollers 27 and 28 together. Vapor applicator 16 is composed of a shield31 and an outlet tube 14. Outlet tube 14 extends across the width oftransfer table 15, as does shield 31, and is provided with manyuniformly cut and uniformly spaced outlets facing the direction oftransfer table 15. Outlet tube 14 is connected to vaporizing tower 18through connecting tube 17 which is composed of a single tube lengthextending from vaporizing tower 18 and a joint at which the single tubesplits into 2 tube lengths each of these lengths extending to andterminating at an opposite extremity of outlet tube 14. Vaporizing tower18 stands in water pan 2?. and is surrounded by cloth covering 20. Athermometer 26 is positioned and disposed to indicate the temperature ofthe liquid 25 within vaporizing tower 18 while liquid level indicator 21shows the amount of liquid 25 present. Air pressure is supplied tovaporizing tower 13 by conduit 32 and through bubbler manifold '33.Cooling fan 23 is positioned near vaporizing tower 18.

To place the transfer apparatus in operation air pressure is appliedthrough conduit 32 and through bubbler manifold 33 to vaporizing tower18. This pressure drives vapors of liquid 25 through tube 17 to vaporapplicator 16 where vapors escape through the openings in outlet tube 14and saturate the area below shield 31.

Although vaporizing tower 18 is always connected to outer areas throughthe openings of outlet tube 14, substantially no loss of vapors willresult when the transfer apparatus is not in operation. The vaporsthemselves are generally heavier than air and if pressure is notsupplied through conduit 32, the vapors will not escape upward outofvaporizing tower 1S and out of the openings of outlet tube 14. Of coursea valve or pet-cock may be inserted in tube 17 to further assure thatvapors do not escape.

Sheet 12 carrying powder image 13 moves into rollers 27 and 28 afterpassing beneath the saturated area below shield 31. The vapors of liquid25, vapors which act as a solvent for the image material making up image13, contact image 13 as those areas on surface 12 carrying imagematerial move beneath vapor applicator 16 and are absorbed into theimage material and dissolved therein. After removal from rollers '27 and23, transfer surface 30 is separated from sheet 12 and the vaporsabsorbed by the image material are allowed to evaporate. The image willappear on transfer surface 30 and will be permanently fused to thissurface.

. Liquid 25 should be a volatile liquid, the vapors of which act as asolvent for the materials making up image 13. The particular liquid usedwill depend on the particular image material and generally it can besaid that suitable solvents include, but are in no way limited to,chloroform, carbon tetrachloride, trichloroethylene and otherchlorinated solvents; the various Freons (believed to be fluorinatedlower alkanes); aromatic and aliphatic hydrocarbons such as benzene,toluene, gasoline and gasoline fractions; oxygenated solvents such asethanol, acetone, ethyl acetate and other alcohols, ketones, esters andthe like.

Although it is not intended to limit in any Way this invention, andalthough other explanations are possible, it is now believed that thevapors of liquid 25 act on image 13 thereby causing it to become a moreliquified tacky or adhesive body. If allowed to stand the image wouldfuse into a solid permanent image body and permanently affix itself tosheet 12 on which it rests. However, when subjected to even pressures byrollers 27 and 28, while in contact With transfer surface 30, tackyimage 13 adheres to and thus fuses and permanently affixes itself tothat surface presented to it which will hold the tacky image adhesivelywith more tenacity than the other surface. For example, if sheet 12 isone to which a tacky image will not readily adhere, the even pressureapplied by rollers 27 and 28 will cause transfer surface 30 as Well assheet 12 to be pressed against image 13 with equal force, and whenseparation of sheet 12 from transfer surface 30 is accomplished, imagebody 13 will have transferred to transfer surface 30 and willpermanently aflix and fuse thereon.

To facilitate the transfer of image 13 from sheet 12 to transfer surface30 the relative abilities of the surfaces to hold the image in its tackystate must be taken into account. For example, if both sheet 12 andtransfer surface 30 tend to hold the image with equal holding force, theimage material will divide between the surfaces when sheet 12 andtransfer surface 30 are separated. Another factor which must beconsidered is the cohesive force of the image body itself as it relatesto the adhesive tendencies of the surfaces presented to it, for example,if the adhesive properties of sheet 12 with respect to the, image aregreater than the cohesive forces of the exposed tacky image, a portionof the image body will afiix itself to sheet 1 2 and remain there afterseparation. To avoid such happenings and to bring about completetransfer of image 13 to transfer surface 30, it is desirable that image13 after exposure to image soluble vapors be incompatible with thesurface on which it rests, or sheet 12, and that it associate readilywith the surface against which it is pressed, or transfer surface 30. Byincompatible it is meant that the image material in its tacky state andas it solidifies does not adhere substantially to the surface towardwhich it is incompatible. This incompatibility may be an inherentproperty of the image material with respect to the image-bearing surfaceor it may be accomplished by treatment such as, for example, moisteningthe surface with water.

In the preferred embodiment of this invention, image 11 on surface 10 istransferred to a sheet material carrying a moist and swollen hydrophiliclayer and preferably a gelatin coating. This material carrying a gelatincoating is in this invention sheet 12 which is then pressed againstsurface 10 bringing about a transfer of image 11 to sheet 12 whereonimage 13 is found. In this invention sheet 12 while still damp isinjected into the transfer apparatus and therein subjected to exposureto vapors and pressing betweenrollers 2'7 and 28 against transfersurface 30. Image 13, when exposed to vapors, becomes a sticky, tackyimage body which is immiscible with the damp gelatin layer and WhileWithin and on, it remains a separate body which will readily adhere to asurface presented to it. When this sticky, tacky, adhesive form of imagecontacts transfer surface 30, while between rollers 27 and 28, itadheres with more tenacity to transfer surface 30 than to surface 12. Inthis embodiment, therefore, incompatibility has been accomplished bymeans of iinrniscibility. When separation is accomplished substantiallyall of the image material is transferred to transfer surface 30 on whichit solidifies.

Transfer surface 30 should be any surface to which the image willreadily adhere. This includes, but is in no way limited to papers, Webor sheet materials, coated surfaces, metallic materials, plastics andthe like. In producing lithographic plates according to this invention,fine results have been obtained using grained and ungrained zincsurfaces, grained and ungrained aluminum surfaces, bimetalliclithographic plates, steel, and the like including various otherlithographic plate materials and metals used in template making.

The image may be composed of any material which will fuse to a solid andpermanent image body when exposed to solvent vapors. This includes, butis in no way limited to known xerographic developers such as pigmentedresins including rosin-modified phenol-formaldehyde resins such as aredisclosed in Copley 2,659,670. One such preferred image material of thiskind is available from The Haloid Company, Rochester, NY. under the nameXeroX Toner. When this image material is used it is preferred thattrichloroethylene be employed as liquid 25.

In order to consistently achieve good transfers the vapor temperature asit relates to the image material temperature must be controlled. It hasbeen found that when too little solvent is absorbed by the image, thepowder will not transfer to the transfer surface, while when too muchsolvent is absorbed by the image material, the image becomes too fluidand spreads as it is squeezed between the rollers.

If the temperature of the image material as it relates to thetemperature of the vapors is too low, the vapor condenses readily on theimage particles, causing the image to absorb too much solvent, therebymaking the image too fluid to transfer properly. On the other hand ifthe temperature of the image material in respect to the temperature ofthe vapors is too high, then suflicient solvent is not absorbed and theimage not transfer. It is preferred that condensation be avoided as anaid to absorption of the proper amount of solvent in the image materialsand as a means of promoting eflicient transfers.

When condensation occurs, not only will the image body become too fluid,but droplets of liquid 25 will form on the matrix on which, or in which,the image body rests. These droplets will appear both unevenly in amountand without uniformity of position. They have no beneficial effect tothe process of transfer but can act detrimentally, as for example byspreading unevenly portions of the image or making portions of the imageae'eaoss too fluid to transfer, or by somehow reacting with the matrixitself or the like. This is another reason condensation should beavoided.

It has been found that condensation of vapors striking the imageparticles and the matrix is prevented when liquid 25 is at a temperatureof from to 20 F. cooler than the temperature of the image material andthe matrix which generally means 10 to 20 F. cooler than roomtemperature and preferably F. cooler.

One very convenient means of temperature control is accomplished bystanding vaporizing tower 18 in water pan 22 so that cooling clothabsorbs water and becomes saturated. -Fan 23, which is manuallycontrolled, is allowed to blow toward cooling cloth 20 until thetemperature as read on thermometer 26 of liquid is within the desiredrange. Fan 23 is turned off and on as desired, thereby keeping thetemperature of liquid 25 in the preferred range while the transferapparatus is in use. Thermostatic means, of course, could be devised tooperate the fan automatically, and also other ways of controlling thevapor temperature are possible and are intended to be encompassed Withinthe scope of this invention.

It has also been found that the concentration of vapor in the vapor airmixture has a decided effect on transfer. Using trichloroethylene as thevapor, a suitable range appears to be a concentration of between 15 to50 percent of vapor in air, and optimum results have been attained usinga concentration of 25 percent vapor by weight in air.

The air pressure supplied through conduit 32 is dependent on a number offactors such as for example the desired saturation of the vapors in airbeneath shield 32, the rate of flow required to maintain saturation, thegeometry of the tubes 17 and 14 and the openings of outlet tube 14 andthe like. The preferred air pressure supplied should produce air flowthrough vaporizing tower 18 at a rate of about 20 to 40 liters perminute.

For best results the image material should be exposed for a closelycontrolled time to the vapors. Sheet 12 moves under vapor applicator 16as it is drawn through rollers 27 and 28. Preferably these rollers aredriven by a motor (not shown) at a rate causing sheet 12 to move undervapor applicator 16 so that it takes the desired amount of time forimage material to enter and pass under and leave the area directly undervapor applicator 16. Using trichloroethylene vapors on known xerographicdevelopers requires an exposure of from 1 to 3 seconds, and preferablyfor 2 seconds, and exposure generally Will vary depending on the vaporsused, the image material, the concentration and the like.

Rollers 27 and 28 may be rubber rollers or the like. The amount ofpressure they exert will depend on many factors, such as for example theimage material, the transfer surface, sheet 12, the room temperature andthe like. per linear inch has been found to produce good transfers wherenormal xerographic developers are exposed to trichloroethylene vaporsWithin the other preferred limitations of this invention.

Following the movement of transfer surface 30 and sheet 12 throughrollers 27 and 2S, sheet 12 is separated out of contact with transfersurface 30 leaving a transferred image on transfer surface 30. A timedelay of a few seconds and preferably from 4 to 8 seconds is desirablebefore the transferred image is used for example as the image to beinked on a lithographic plate. This time delay will allow absorbedvapors to evaporate thereby solidifying the image. Generally the fusedimage will need no further treatment; however, for some applications ofthe transferred image it may be desirable to further assure permanencethrough exposure to heat. It is pointed out that usually any time delaynecessary for the image to solidify and to permanently fuse will be lessthan the time it takes to attach transfer surface 30 to other equipmentfor further utilization and so generally Generally a force of from 2 to10 pounds provisions for the time The final image is a fused permanentimage which is permanently aflixed to transfer surface 30, whether thissurface be conductive or not, and whether it be rigid or not.

Although this invention has been described in terms of specificembodiments, it is intended to broadly cover this invention the scopeand spirit of the appended claims.

What is claimed is:

l. A method of transferring a tackifiable developed xerographic powderimage, the steps comprising exposing said image resting on a supportbase to vapors of a solvent for the image material, said support basebeing incompatible with said image material when said image material isin a tacky state, pressing said support base carrying said image afterexposure to said vapors and while in a tacky state against a transfersurface of a transfer member with said tacky image between said supportbase and said transfer surface, said transfer surface comprising amaterial to which said tacky image adheres tenaciorusly causing adhesionof the developed and tacky image to said surface while said support baseand transfer surface are pressed together, separating said support basefrom. said transfer surface with said image adhering to said transfersurface, and solidifying said exposed image by evaporating said vaporsfrom the image material.

2. A method of forming a fused transferred permanent xerographic imageon a surface comprising transferring a developed xerographic image oftackifiable electroscopic powder particles on a xerographic plate to asupport base carrying a water impregnated hydrophilic layer by pressingsaid image against said hydrophilic layer, exposing said transferredpowder image on said support base to vapors of a solvent for saidelectroscopic powder particles to render said powder image tacky, saidvapors being held at a cooler temperature than said powder particles,pressing said support base carrying the tacky xerographic image againsta transfer surface of a transfer member with said tacky image betweensaid transfer member and said support base between rollers, said tackyimage holding with greater tenacity to said transfer surface than tosaid hydrophilic layer, separating said support base from said transfersurface with said image on said transfer surface, and solidifying saidimage into a fused transferred permanent xerographic image body on saidtransfer surface by allowing said solvent vapors to evaporate from saidimage body.

3. A method of transferring a tack-ifiable developed xerogr-aphic powderimage to a substantially rigid surface comprising transferring adeveloped xenographic image to a support base characterized by the factthat the image body after exposure to solvent vapors is incompatiblewith said support base while in a tacky condition, exposing said imageon said support base to trichloro'ethylene vapors said vapors being heldat a temperature differential of from 10 to 20 F. cooler than said imagematerial, each portion of said image material being exposed to saidvapors for a maximum of 3 seconds and for sufiicient time to cause saidimage to become tacky, pressing said tacky image on said support baseagainst the surface of a substantially rigid member using a maximum of10 pounds of force per linear inch, said tacky image being attractedwith greater tenacity to said surface of said rigid member than to thesurface of said support base, separating said support base from saidsubstantially rigid member with said image adhering to said surface ofsaid rigid member, and allowing said vapors to evaporate from said imagebody thereby forming a permanently fused image on said substantiallyrigid memher.

4. A method of transferring a tackifiable developed xerographic powderimage to a conductive rigid member 7 comprising transferring saiddeveloped xerographic image to a support base characterized by the factthat the image body after exposure to solvent vapors and while in atacky condition is immiscible with said support base, ex-

posing said image on said support base to solvent vapors V to rendersaid image tacky, pressing said tacky image on said support base againsta conductive rigid member using a force of from 2 to 10 pounds perlinear inch, said conductive rigid member having characteristics to holdtenaciously said tacky image causing said image to bond to said n'gidmember while said tacky image is pressed against said rigid member, andseparating said support base from said conductive rigid member therebyforming a permanently fused image on said conductive rigid memher.

5. In a method of forming a metal base lithographic plate wherein axenographic plate is charged exposed developed with powder particles andthe developed powder image is transferred to a support base theimprovement comprising using as the support base a gelatin coated paperwhich has been wetted and blotted to remove excess water and thenpressed against said xerographic plate carrying said developed image toeffect a transfer, exposing said gelatin coated paper carrying saidimage while still in a damp condition to trichloroethylene vapors torender said developed powder image tacky, said vapors being held at atemperature differential of about F. cooler than said image material,said tacky image being immiscible with said support base, pressing saiddamp gelatin coated paper carrying said tacky image against a metal baselithographic plate immediately after exposure to said vapors with saidtacky image between said plate and said support base, said plate havingsurface characteristics to hold said tacky image tenaciously whencompared to the immiscibility'of said tacky image with said supportbase, separating said gelatin coated paper from said lithographic platecausing said tacky image to adhere to said plate, and evaporating saidvapors from the image material thereby solidifying and permanentlyforming said image on said lithographic plate.

6. A method of transferring a developed xerographic image, which imagecomprises a tackifiable resin powder in image configuration, the stepscomprising forming said developed xerographic image on an image-bearingmemher having a surface incompatible with a solvent-tackified resinimage, tackifying said xerographic image by exposing the image to vaporsof a volatile solvent for said image to cause absorption of solvent intothe image, pressing said image-bearing surface against animage-receiving member while said image is in a tacky condition withsaid image between said image-bearing member and said image receivingmember, the surface of said image receiving member in contact with saidtacky image being characterized by its ability to hold said tacky imagetenaciously as compared to the incompatibility between said tacky imageand said ima-gebearing surface to cause said tacky image to adhere tosaid image receiving member, separating the image-bearing member fromthe imagereceiving member with said image now adhering to said imagereceiving member and solidifying the image by evaporating the solventtherefrom.

7. A method of transferring a tackifiable developed xerographic powderimage to a lithographic plate, which image comprises a resin powder inimage configuration which becomes tacky on exposure totrich-loroethylene vapors, the steps comprising forming said developedXerographic image on damp gelatimcoated paper, tackifying saidxerographic image by exposing the image to a substantially saturatedatmosphere of trichloroethylene vapors to cause absorption of saidtrichloroethylene vapors into the image, pressing said dampgelatin-coated paper carrying said tacky image against the lithographicplate, said plate being characterized by its ability to hold said imagetenaciously as compared to the immiscibility of said tacky image withsaid damp gelatin-coated paper causing said tacky image to adhere tosaid plate when pressed against said plate between said gelatin-coatedpaper and said plate, separating the gelatin-coated paper from thelithographic plate with the transfer image adhering to said plate, andsolidifying the image.

References Cited in the file of this patent UNITED STATES PATENTS655,735 Reid Aug. 14, 1900 2,271,491 Rathke Jan. 27, 1942 2,297,691Carlson Oct. 6, 1942 2,299,974 Grosbecker Oct. 27, 1942 2,624,652Carlson Jan. 6, 1953 2,637,651 Copley May 5, 1953 2,661,289 Mayo et a1.Dec. 1, 1953 2,726,166 Greaves Dec. 6, 1955

